The main differences are that the change in graphic cards. G750JM comes with GTX 860M(2GB DDR5) and G750JS comes with GTX 870M(3GB DDR5)
the other noticeable change is that of the HDD. G750JM has 1TB (5400 rpm) and G750JS has 1TB(7200 rpm).Suprisingly both are at the same price on Newegg at $1199.
I'm waiting for any other noticeable changes and did anyone have any problems with the G750JS model? I'm planning to buy that in a few days.!